R-Spondin 2 (RSPO2)

R-spondins (RSPOs), such as RSPO2, are secreted proteins that regulate beta-catenin (CTNNB1) signaling. Xenopus and human RSPO2 enhanced mouse Wnt3a signaling in transfected human embryonic kidney cells. C-terminally truncated Xenopus Rspo2, but not the full-length protein, was secreted from cells and retained its activity. Mutation analysis showed that the TSP1 domain of Xenopus Rspo2 was dispensable for activity, but the furin domains were required. RT-PCR analysis showed that Xenopus embryos injected with Wnt8 or beta-catenin induced Rspo2 and Rspo3. Overexpression of Rspo2 in Xenopus activated the Wnt/beta-catenin pathway upstream of dishevelled (DVL1), interfered with Tgfb-type growth factors, and promoted myogenesis.